What is this ammonite piece?

[Mochaccino]

Anyone know what species of ammonite this is? I see those suture patterns so it does seem like some sort of ammonite. Seems to be about 2 in long. Since it has an open coil is it a possible heteromorph (or just a broken homomorph)?

 

 

 

Edited December 21, 2021 by Mochaccino

[Rockwood]

31 minutes ago, Mochaccino said:

heteromorph

'Pretty sure of that at least.

[R0b]

Can’t help you but those who can would need more information. As much information as possible about the origin of this piece. Country, region, location, formation.

[caterpillar]

Maybe Didymoceras

[Mochaccino]

2 hours ago, R0b said:

Can’t help you but those who can would need more information. As much information as possible about the origin of this piece. Country, region, location, formation.

 

19 minutes ago, caterpillar said:

Maybe Didymoceras

 

2 hours ago, Rockwood said:

'Pretty sure of that at least.

 

Thanks, unfortunately I don't have any other information available...However looking at the ribbing, color and sutures:

 

 

 

it looks very similar to the middle section of this Didymoceras nebrascense photo I found on Wikipedia, so perhaps indeed a Didymoceras?

 

[Ludwigia]

Didymoceras is a logical possibility, although there are a number of other genera which might fit, but without any background on the provenance it will probably have to remain with a large question mark as far as scientific confirmation is concerned.

[Mochaccino]

46 minutes ago, Ludwigia said:

Didymoceras is a logical possibility, although there are a number of other genera which might fit, but without any background on the provenance it will probably have to remain with a large question mark as far as scientific confirmation is concerned.

Just heard from the seller that it was apparently dug from Madagascar, does that inform the genus further?

[Ludwigia]

2 minutes ago, Mochaccino said:

Just heard from the seller that it was apparently dug from Madagascar, does that inform the genus further?

 

Not really, since he gives no specific location or precise stratigraphy.

[Mochaccino]

23 minutes ago, Ludwigia said:

 

Not really, since he gives no specific location or precise stratigraphy.

I see, what are some other genera that might fit besides Didymoceras? Or is that list too extensive?

[Ludwigia]

19 minutes ago, Mochaccino said:

I see, what are some other genera that might fit besides Didymoceras? Or is that list too extensive?

 

I would suggest to you that you research that yourself.

[RJB]

3 hours ago, Mochaccino said:

Just heard from the seller that it was apparently dug from Madagascar,

Im not saying that it wasn't dug from Madagascar, but it doesn'd look like Madagascar material?

 

RB

[Mochaccino]

5 hours ago, Ludwigia said:

 

I would suggest to you that you research that yourself.

 

I was asking because you told me "there are a number of other genera which might fit" , and I wondering what other ones you had in mind. Your response honestly seems a little strange to me considering I specifically posted in the ID thread asking for help, provided info to the best of my knowledge, and suggested my best guess after some of my own searching.

Edited December 21, 2021 by Mochaccino

[Mochaccino]

1 hour ago, RJB said:

Im not saying that it wasn't dug from Madagascar, but it doesn'd look like Madagascar material?

 

RB

 

Hmm, the seller honestly seems pretty clueless so I wouldn't be surprised if he/she were wrong on even the source. What specific aspects of this specimen make you say that? I do think the color/texture of the shell doesn't seem anything like the Madagascar heteromorphs such as Nostoceras...that shiny white/grey texture seems like the Russian ammonites, or as I said the Didymoceras nebrascanse specimen, which doesn't seem to be found in Madagascar.

[Ludwigia]

23 minutes ago, Mochaccino said:

 

I was asking because you told me "there are a number of other genera which might fit" , and I wondering what other ones you had in mind. Your response honestly seems a little strange to me considering I specifically posted in the ID thread asking for help, provided info to the best of my knowledge, and suggested my best guess after some of my own searching.

 

I just wanted to help out your learning curve. Looks like you've already covered as much ground as I would have.

[FossilDAWG]

There are a number of similar looking heteromorphs, including Didymoceras, Nostoceras, Bostrychoceras, Eubostrychoceras, etc.  The first two in particular are hard to differentiate, especially from fragments of the living chamber such as your specimen.  The generic assignment of some species has gone back and forth between the two.  Differentiation depends on the earliest whorls (which are fragile and not often preserved) as well as features such as whether or not the whorls of the turreted part are in contact. In Nostoceras the whorls are in contact and each whorl leaves an impression on the next up until the last mature whorl.  In Didymoceras the turret is more open, with the whorls loosely coiled and not contacting or just touching subsequent whorls.  Some Didymoceras species do have a mix of some whorls in contact and others loosely coiled.  Both genera have a mature whorl that turns down from the turret, then makes a hook so the aperture ends up facing back up towards the turreted part of the shell.  Individual species are differentiated based on ornament (rib density and sculpture, nodes and spines etc) as well as how open vs tightly coiled the turret is.

 

Nostoceras malagasyense is known from Madagascar and specimens, often highly "restored" (=carved), are commercially available.  It is likely that Didymoceras occurs there as well but I don't know of specific references regarding that.  Your specimen looks to me to have a mode of preservation that is different than the material of Nostoceras malagasyense that I have seen, which have a brown calcitic shell preserved in a calcarious sandstone.  Your specimen looks more like US Pierre Shale material to me.  However I certainly am not familiar enough with Madagascar geology to be certain the specimen doesn't come from there.

 

Without knowing the provenience for certain, the most safe ID would be "nostocerid ammonite".

 

Don

[FossilDAWG]

Actually just found a publication on the heteromorphs from Madagascar: Klinger et al 2007.

 

Their Figure 1 of Nostoceras malagasyense might be a good match for your specimen.

 

Don

 

 

[Mochaccino]

2 hours ago, FossilDAWG said:

There are a number of similar looking heteromorphs, including Didymoceras, Nostoceras, Bostrychoceras, Eubostrychoceras, etc.  The first two in particular are hard to differentiate, especially from fragments of the living chamber such as your specimen.  The generic assignment of some species has gone back and forth between the two.  Differentiation depends on the earliest whorls (which are fragile and not often preserved) as well as features such as whether or not the whorls of the turreted part are in contact. In Nostoceras the whorls are in contact and each whorl leaves an impression on the next up until the last mature whorl.  In Didymoceras the turret is more open, with the whorls loosely coiled and not contacting or just touching subsequent whorls.  Some Didymoceras species do have a mix of some whorls in contact and others loosely coiled.  Both genera have a mature whorl that turns down from the turret, then makes a hook so the aperture ends up facing back up towards the turreted part of the shell.  Individual species are differentiated based on ornament (rib density and sculpture, nodes and spines etc) as well as how open vs tightly coiled the turret is.

 

Nostoceras malagasyense is known from Madagascar and specimens, often highly "restored" (=carved), are commercially available.  It is likely that Didymoceras occurs there as well but I don't know of specific references regarding that.  Your specimen looks to me to have a mode of preservation that is different than the material of Nostoceras malagasyense that I have seen, which have a brown calcitic shell preserved in a calcarious sandstone.  Your specimen looks more like US Pierre Shale material to me.  However I certainly am not familiar enough with Madagascar geology to be certain the specimen doesn't come from there.

 

Without knowing the provenience for certain, the most safe ID would be "nostocerid ammonite".

 

Don

Thank you so much for this detailed lesson. Learning about the specific features of differentiation is quite fascinating and very informative. I've been looking at a lot of Nostoceras photos due to my heteromorph obsession and I agree this looks differently preserved than all the other ones I've seen. At least I haven't seen that coloration or suture pattern on any Nostoceras malagasyense, but perhaps this is a matter of site. I guess the best guess would indeed be just Nostoceratid heteromorph ammonite, possibly Nostoceras or Didymoceras.

Edited December 21, 2021 by Mochaccino

[RJB]

17 hours ago, Mochaccino said:

What specific aspects of this specimen make you say that?

I know a guy who takes pieces of these heteromorphs and frankinsteins them together to make complete specimens, so ive seen a lot of this kind of material.  Ive also seen lots and lots of the ones that come from Madagascar.  The one you have looks very much like it came from the Missouri River Breaks which is in Montana. Not saying this is so, just a guess.

 

RB 

[Mochaccino]

15 hours ago, RJB said:

I know a guy who takes pieces of these heteromorphs and frankinsteins them together to make complete specimens, so ive seen a lot of this kind of material.  Ive also seen lots and lots of the ones that come from Madagascar.  The one you have looks very much like it came from the Missouri River Breaks which is in Montana. Not saying this is so, just a guess.

 

RB 

Interesting, is that part of the Pierre Shale or a separate region? (EDIT: looks like Pierre Shale is South Dakota, and Montana has the Bearpaw shale?) Seems like based on the opinions here regarding material/preservation on this one that it actually isn't from Madagascar, which might exclude Nostoceras malagasyense.

Edited December 23, 2021 by Mochaccino